CMP (chemical mechanical polishing) is a technique of planarizing surfaces by bringing a processing surface of a substrate to be polished into contact with a polishing pad, supplying a polishing liquid to a contact portion therebetween, and moving them relatively, thereby allowing uneven portions on the surface of the substrate to be reacted chemically and removed mechanically.
Patent Document 1 discloses, as a polishing agent for forming a shallow trench isolation structure, a CMP polishing agent that includes: a cerium oxide particle; a dispersant; a water-soluble organic low-molecule additive having an anionic group selected from a free —COOM group, a phenolic OH group, a —SO3M group, an —OSO3H group, a —PO4M2 group, and a —PO3M2 group (wherein M is H, NH4, or a metal atom such as Na or K); and water.